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CHAPTER 2
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EXPERIMENTAL PROCEDURES
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2.1
The instrumentation involved in Operation Ivy was designed to accomplish four objectives:
(1) to suspend pressure and thermai-radiation probes in the blast field by deploying parachuteborne canisters from two B-29 aircraft, (2) to receive the ‘adio telemetry signal (data intelljgence) from the paract.ute-borne canisters, (3) to record the arrival time of the peak biast
overpressure at each canister, and (4) to record the pressure and thermal data.
A general description of the instrumentation for pressure and a'titude determinations and
thermal measurements and of the radio telemetry system is presented in this section. Fora
detailed description of the basic design of the canisier instrumentation and the radio telemetry
system, reference should be nade to Operation Jangle Report, Project 1.3c;! Bencix Aviation
Corp. reports, the operation and maintenan~e instructions;* and the Y-11600 telemetering cani-
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2.1.1
Pressure and Thermal Transduceis
The pressure transducers are a diaphragm type in which the displacementof the diaph.agm
produced by a difference in pressure on opposite sides changes the air gap in a magnets circenit. The resulting variation of inductance causes a variation in the frequensy of the oscillator
channel to which it is connected.
In the case of the differential-pressure transducers, one side of the diaphragm is vented to
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INSTRUMENTATION
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the atmosprere through a probe about 2 ft long mounted on the nose of the canister. The «iher
side of the diaphragm is connected to a reference chamber with a volume of about 125 cu in.,
which in turn is vented to the atmosphere tirough a slow leak consisting of a 7-ft length of
1/8-in.-O.D. copper tubing. This provides a means of equalizing the pressure on both sides of
the diaphragm during parachute descent, but it allows differential pressures of shert duration
to be measured before appreciable equalization of pressures takes place. In order to obtain
the full pressure-time curveof the blast pulse, the reference chamber vent is sealz2 by a
solenoid- operated valve, which is activated by the initial blast overpressure. When tas valve
fails to operate, an accurate pressure-time curve is not obtained, but the indiceted peak overpressure ir not affected (Sec. 3.1.1).
The altimeter pressure transducer is similar to the differential-pressure gauges except
that the case body on one side of the diaphragm is evacuated and sealed and the othes side is
vented to the atmospherein the open afterbody of the canister.
The thermal transducer is a thermocouple which has been aesignated a: type H-2 by tie
manufacturer, The Eppley Uaboratory, Inc., of Newport, R. J. The construction is shown in
Fig. 2.1. A couple of platinum-rhodium alloy and gold-palladium wires, 1.5 mils in diameter,
was form:d with the exposed hot junction in an approximately spherical bead 10 mils in diam-
11
RESTRICTED DATA QM SECURITY INFORMATION
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